Multi-walled carbon nanotubes/carbon black/rPLA for high-performance conductive additive manufacturing filament and the simultaneous detection of acetaminophen and phenylephrine.

The combination of multi-walled carbon nanotubes (MWCNT) and carbon black (CB) is presented to produce a high-performance electrically conductive recycled additive manufacturing filament. The filament and subsequent additively manufactured electrodes were characterised by TGA, XPS, Raman, and SEM and showed excellent low-temperature flexibility. The MWCNT/CB filament exhibited an improved electrochemical performance compared to an identical in-house produced bespoke filament using only CB. A heterogeneous electrochemical rate constant, [Formula: see text] of 1.71 (± 0.19) × 10-3 cm s-1 was obtained, showing an almost six times improvement over the commonly used commercial conductive CB/PLA. The filament was successfully tested for the simultaneous determination of acetaminophen and phenylephrine, producing linear ranges of 5-60 and 5-200 µM, sensitivities of 0.05 µA µM-1 and 0.14 µA µM-1, and limits of detection of 0.04 µM and 0.38 µM, respectively. A print-at-home device is presented where a removable lid comprised of rPLA can be placed onto a drinking vessel and the working, counter, and reference components made from our bespoke MWCNT/CB filament. The print-at-home device was successfully used to determine both compounds within real pharmaceutical products, with recoveries between 87 and 120% over a range of three real samples. This work paves the way for fabricating new highly conductive filaments using a combination of carbon materials with different morphologies and physicochemical properties and their application to produce additively manufactured electrodes with greatly improved electrochemical performance.

Using low-cost disposable immunosensor based on flexible PET screen-printed electrode modified with carbon black and gold nanoparticles for sensitive detection of SARS-CoV-2.

To help meet the global demand for reliable and inexpensive COVID-19 testing and environmental analysis of SARS-CoV-2, the present work reports the development and application of a highly efficient disposable electrochemical immunosensor for the detection of SARS-CoV-2 in clinical and environmental matrices. The sensor developed is composed of a screen-printed electrode (SPE) array which was constructed using conductive carbon ink printed on polyethylene terephthalate (PET) substrate made from disposable soft drink bottles. The recognition site (Spike S1 Antibody (anti-SP Ab)) was covalently immobilized on the working electrode surface, which was effectively modified with carbon black (CB) and gold nanoparticles (AuNPs). The immunosensing material was subjected to a multi-technique characterization analysis using X-ray diffraction (XRD), transmission electron microscopy (TEM), and scanning electron microscopy (SEM) with elemental analysis via energy dispersive spectroscopy (EDS). The electrochemical characterization of the electrode surface and analytical measurements were performed using cyclic voltammetry (CV) and square-wave voltammetry (SWV). The immunosensor was easily applied for the conduct of rapid diagnoses or accurate quantitative environmental analyses by setting the incubation period to 10 min or 120 min. Under optimized conditions, the biosensor presented limits of detection (LODs) of 101 fg mL-1 and 46.2 fg mL-1 for 10 min and 120 min incubation periods, respectively; in addition, the sensor was successfully applied for SARS-CoV-2 detection and quantification in clinical and environmental samples. Considering the costs of all the raw materials required for manufacturing 200 units of the AuNP-CB/PET-SPE immunosensor, the production cost per unit is 0.29 USD.

Development of New Simple Compositions of Silver Inks for the Preparation of Pseudo-Reference Electrodes.

Silver materials are known to present excellent properties, such as high electrical and thermal conductivity as well as chemical stability. Silver-based inks have drawn a lot of attention for being compatible with various substrates, which can be used in the production uniform and stable pseudo-reference electrodes with low curing temperatures. Furthermore, the interest in the use of disposable electrodes has been increasing due to the low cost and the possibility of their use in point-of-care and point-of-need situations. Thus, in this work, two new inks were developed using Ag as conductive material and colorless polymers (nail polish (NP) and shellac (SL)), and applied to different substrates (screen-printed electrodes, acetate sheets, and 3D-printed electrodes) to verify the performance of the proposed inks. Measurements attained with open circuit potential (OCP) attested to the stability of the potential of the pseudo-reference proposed for 1 h. Analytical curves for ß-estradiol were also obtained using the devices prepared with the proposed inks as pseudo-references electrodes, which presented satisfactory results concerning the potential stability (RSD < 2.6%). These inks are simple to prepare and present great alternatives for the development of pseudo-reference electrodes useful in the construction of disposable electrochemical systems.

Waterproof paper as a new substrate to construct a disposable sensor for the electrochemical determination of paracetamol and melatonin.

Disposable electrochemical sensors using sustainable and cheap materials are an exciting alternative to produce new kinds of sensing platforms. Waterproof paper (WP) is a biodegradable and biocompatible material that allows dropped of the sample on its surface without absorption by fibers. Also, WP can be used for miniaturized sensors construction. In this work, a conductive ink was produced with nail polish and graphite powder, using the WP as the sensor substrate for paracetamol (PAR) and melatonin (MEL) voltammetric determination. PAR is a pharmaceutical commonly used in high doses for the relief of pain and fever, and MEL is a hormone related to several diseases besides a direct relation to sleep quality. Using differential pulse voltammetry for PAR determination, the WP sensor showed a linear response in the concentration ranging from 0.50 µmol L-1 to 100 µmol L-1 with a limit of detection (LOD) of 53.6 nmol L-1. Square wave voltammetry was applied for MEL determination, and the proposed electrode presented linear response ranging from 0.80 µmol L-1 to 100 µmol L-1 and LOD of 32.5 nmol L-1. The sensor showed excellent repeatability and reproducibility for consecutive measurements. Then, the disposable WP sensor was successfully applied in the determination of PAR and MEL in pharmaceutical and biological samples, with recovery values, above 91.1%. The described architecture allowed the manufacture of a disposable, simple, and low-cost electroanalytical device that can be used for electrochemical sensing.